1. Field of the Invention
The present invention relates to a flight state detection apparatus and a flight state detection method that is capable of detecting the flight state of a micro object in flight.
2. Description of the Related Art
For example, various methods of manufacturing a so-called DNA chip (a DNA micro array) are well known. The DNA chip is generally constructed by arraying and fixing micro spots of several thousand to ten thousand or more kinds of different DNA pieces on a substrate, such as microscope slide glass, with high density.
As examples of the DNA chip manufacturing methods, there have been proposed methods of manufacturing a DNA chip using a micropipette for ejecting drops having micro volume (for example, see the following Patent References 1 and 2). The micropipette includes an injection port for injecting a sample solution from the outside, a cavity for allowing the sample solution injected from the injection port to be filled therein, an ejection port communicating with the cavity, and a piezoelectric/electrostrictive element constructed to change the interior volume of the cavity such that the sample solution can be ejected from the ejection port.
According to the above-described DNA chip manufacturing methods, the interior volume of the cavity is changed by the driving operation of the piezoelectric/electrostrictive element. As the interior volume of the cavity is changed, the sample solution moves from the cavity to the ejection port in the form of a streamline flow. That is, a predetermined amount of the sample solution is delivered from the cavity to the ejection port. As the predetermined amount of the sample solution is ejected from the ejection port, micro drops of the sample solution are generated. The micro drops of the sample solution ejected from the micropipette are attached to the substrate, and the micro drops are arrayed and fixed on the substrate as micro spots. In this way, the DNA chip is manufactured.
An apparatus constructed to eject a micro object (hereinafter, simply referred to as a “micro object ejection apparatus”), such as the micropipette used in the DNA chip manufacturing method as described above, may be utilized in various technical fields.
Furthermore, a mass sensor constructed to measure the mass of this kind of micro object has been proposed (for example, see the following Patent Reference 3). In the case that the micro object is attached to a vibrating plate, on which the piezoelectric/electrostrictive element is disposed, the mass sensor serves to measure the change of the resonant frequency of the vibrating plate, which is caused by the mass change of the vibrating plate due to the attachment of the micro object to the vibrating plate, whereby the mass change of the vibrating plate (i.e., the mass of the micro object) is measured.
[Patent Reference 1] Japanese Unexamined Patent Publication No. 2001-124789
[Patent Reference 2] Japanese Unexamined Patent Publication No. 2001-186881
[Patent Reference 3] Japanese Unexamined Patent Publication No. 2000-180250
In this kind of micro object ejection apparatus, the dried and hardened portion of the micro object or foreign matter may be attached around the ejection port, and, as a result, the ejection port may be obstructed. In this case, the micro object may not be accurately ejected toward a predetermined position to which the micro object is to be ejected (for example, see columns [0010] and [0019] of Patent Reference 1).
Also, the detection of the flight state of the micro object using the mass sensor as described in Patent Reference 3 may only be applied to a micro object which is attached to the vibrating plate during a certain period of time (a period of time that the change of the resonant frequency can be measured). Furthermore, in the detection of the flight state using the mass sensor, when the micro object is intermittently ejected from the same micro object ejection apparatus by predetermined periods, it is difficult to continuously detect the flight state of the micro object using the same mass sensor.